/*
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at 
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *  
 */

using System;
using java = biz.ritter.javapi;
using org.apache.commons.collections;

namespace org.apache.commons.collections.functors
{

    /**
     * Transformer implementation calls the transformer whose predicate returns true,
     * like a switch statement.
     * 
     * @since Commons Collections 3.0
     * @version $Revision$ $Date$
     *
     * @author Stephen Colebourne
     */
    public class SwitchTransformer : Transformer, java.io.Serializable
    {

        /** Serial version UID */
        private static readonly long serialVersionUID = -6404460890903469332L;

        /** The tests to consider */
        private readonly Predicate[] iPredicates;
        /** The matching transformers to call */
        private readonly Transformer[] iTransformers;
        /** The default transformer to call if no tests match */
        private readonly Transformer iDefault;

        /**
         * Factory method that performs validation and copies the parameter arrays.
         * 
         * @param predicates  array of predicates, cloned, no nulls
         * @param transformers  matching array of transformers, cloned, no nulls
         * @param defaultTransformer  the transformer to use if no match, null means return null
         * @return the <code>chained</code> transformer
         * @throws IllegalArgumentException if array is null
         * @throws IllegalArgumentException if any element in the array is null
         */
        public static Transformer getInstance(Predicate[] predicates, Transformer[] transformers, Transformer defaultTransformer)
        {
            FunctorUtils.validate(predicates);
            FunctorUtils.validate(transformers);
            if (predicates.Length != transformers.Length)
            {
                throw new java.lang.IllegalArgumentException("The predicate and transformer arrays must be the same size");
            }
            if (predicates.Length == 0)
            {
                return (defaultTransformer == null ? ConstantTransformer.NULL_INSTANCE : defaultTransformer);
            }
            predicates = FunctorUtils.copy(predicates);
            transformers = FunctorUtils.copy(transformers);
            return new SwitchTransformer(predicates, transformers, defaultTransformer);
        }

        /**
         * Create a new Transformer that calls one of the transformers depending 
         * on the predicates. 
         * <p>
         * The Map consists of Predicate keys and Transformer values. A transformer 
         * is called if its matching predicate returns true. Each predicate is evaluated
         * until one returns true. If no predicates evaluate to true, the default
         * transformer is called. The default transformer is set in the map with a 
         * null key. The ordering is that of the iterator() method on the entryset 
         * collection of the map.
         * 
         * @param predicatesAndTransformers  a map of predicates to transformers
         * @return the <code>switch</code> transformer
         * @throws IllegalArgumentException if the map is null
         * @throws IllegalArgumentException if any transformer in the map is null
         * @throws ClassCastException  if the map elements are of the wrong type
         */
        public static Transformer getInstance(java.util.Map<Object, Object> predicatesAndTransformers)
        {
            Transformer[] transformers = null;
            Predicate[] preds = null;
            if (predicatesAndTransformers == null)
            {
                throw new java.lang.IllegalArgumentException("The predicate and transformer map must not be null");
            }
            if (predicatesAndTransformers.size() == 0)
            {
                return ConstantTransformer.NULL_INSTANCE;
            }
            // convert to array like this to guarantee iterator() ordering
            Transformer defaultTransformer = (Transformer)predicatesAndTransformers.remove(null);
            int size = predicatesAndTransformers.size();
            if (size == 0)
            {
                return (defaultTransformer == null ? ConstantTransformer.NULL_INSTANCE : defaultTransformer);
            }
            transformers = new Transformer[size];
            preds = new Predicate[size];
            int i = 0;
            for (java.util.Iterator<Object> it = (java.util.Iterator<Object>)predicatesAndTransformers.entrySet().iterator(); it.hasNext(); )
            {
                java.util.MapNS.Entry<Object, Object> entry = (java.util.MapNS.Entry<Object, Object>)it.next();
                preds[i] = (Predicate)entry.getKey();
                transformers[i] = (Transformer)entry.getValue();
                i++;
            }
            return new SwitchTransformer(preds, transformers, defaultTransformer);
        }

        /**
         * Constructor that performs no validation.
         * Use <code>getInstance</code> if you want that.
         * 
         * @param predicates  array of predicates, not cloned, no nulls
         * @param transformers  matching array of transformers, not cloned, no nulls
         * @param defaultTransformer  the transformer to use if no match, null means return null
         */
        public SwitchTransformer(Predicate[] predicates, Transformer[] transformers, Transformer defaultTransformer)
            : base()
        {
            iPredicates = predicates;
            iTransformers = transformers;
            iDefault = (defaultTransformer == null ? ConstantTransformer.NULL_INSTANCE : defaultTransformer);
        }

        /**
         * Transforms the input to result by calling the transformer whose matching
         * predicate returns true.
         * 
         * @param input  the input object to transform
         * @return the transformed result
         */
        public Object transform(Object input)
        {
            for (int i = 0; i < iPredicates.Length; i++)
            {
                if (iPredicates[i].evaluate(input) == true)
                {
                    return iTransformers[i].transform(input);
                }
            }
            return iDefault.transform(input);
        }

        /**
         * Gets the predicates, do not modify the array.
         * 
         * @return the predicates
         * @since Commons Collections 3.1
         */
        public Predicate[] getPredicates()
        {
            return iPredicates;
        }

        /**
         * Gets the transformers, do not modify the array.
         * 
         * @return the transformers
         * @since Commons Collections 3.1
         */
        public Transformer[] getTransformers()
        {
            return iTransformers;
        }

        /**
         * Gets the default transformer.
         * 
         * @return the default transformer
         * @since Commons Collections 3.1
         */
        public Transformer getDefaultTransformer()
        {
            return iDefault;
        }

    }
}